This invention relates to electrostatic recording and more particularly relates to an image-receiving sheet adapted to receive on the surface thereof a particle image electrostatically formed on a photoconductive surface and whereon a final colored-image is fixed.
The image-receiving sheet of this invention is used for the electrostatic recording process, for example, such as disclosed in British Pat. No. 1,527,168. In that process there is provided an image composing particle containing a colorless sublimable dye. The image-receiving sheet contains a developer which reacts with the colorless sublimable dye to develop a color. The image composed of particles is formed on a photoconductive insulating surface by a suitable electrostatic method and then are transferred to the image-receiving sheet. The particles are then heated, whereby the colorless sublimable dye-former present in the particle is sublimed and reacted with the developer present in the image-receiving sheet to develop a color. The remaining parts of the image composing particles are then removed from the surface of the image-receiving sheet. Thus the fixed dye-image is obtained on the image-receiving sheet.
In such process, the following method of forming the particle image is especially useful. The photoconductive surface is charged and the image composing particles are laid uniformly thereon. The image composing particle is transmissive to a light of selected color, i.e., functions as a color filter, further to containing a sublimable dye as above mentioned. The photoconductive surface is exposed to imagewise light through the image composing particles, thereby forming an electrostatic image corresponding to an image of selected color of light. Then the image composing particles in the area where the electrostatic attractive force is weakened in accordance with the electrostatic image are removed, whereby the particle image is obtained. By utilizing such process, a multicolored dye image can be formed through only one exposure as described in British Pat. No. 1,527,168.
As a matter of course the particle image formation according to the usual xerography may be used.
As an image-receiving sheet applicable to the above-mentioned process, there has been proposed a structure such that a color forming layer containing a developer material is disposed on a support member such as paper and on the color forming layer is disposed a dielectric surface layer which serves to electrostatically retain the transferred image-composing-particles. The dielectric layer necessarily has a structure such that the sublimed dye gas can pass therethrough to the color forming layer. Therefore the surface resistivity of the dielectric layer decreases due to moisture absorption under a high humidity atmosphere such as a relative humidity of more than 60%. Thus the electrostatic charge on the dielectric layer is decreased under high humidity, resulting in low efficiency of transfer of the image composing particles from the photoconductive surface to the image-receiving sheet.